Composition for construction of concrete floors, walls or roofs in buildings

ABSTRACT

The present invention discloses the use of a composition including ballast, hydraulic binding agent and water for the construction of concrete floors, walls or roofs in buildings, in which the ballast in the concrete produced from the composition contains a sufficient amount of soap stone to achieve a concrete with higher specific heat capacity compared to common concrete.

FIELD OF THE INVENTION

The present invention relates to the use of a composition comprising ballast, hydraulic binding agent and water for construction of concrete floors, walls or roofs in buildings.

BACKGROUND OF THE INVENTION

With the energy situation of today, it becomes more and more important to produce, handle and save energy in a way that is as harmless to the environment and as cost effective as possible. The energy for heating plays an important role, particularly in countries with a cold climate.

Due to their high thermal capacities, materials such as stone and water accumulate heat well. However, the heat accumulation characteristics differ in substantial extent with different species of stone. Concrete consists mostly (about 75%, e.g. 60-90%) of ballast material (sand, crushed stone, or in some extent crushed concrete) and has a heat capacity of about 0.92 (e.g. 0.90-0.94) kJ/kg·K.

Concrete ballast generally consists of so called gangue or rubble (usually granite or gneiss). Nevertheless, these species of stone have a relatively poor heat-storing capacity. Other species of stone with better heat-storing capacities are known, but are generally not used as ballast in concrete. The group of species of stone that pass under the term of “soap stone” has excellent heat-storing capacity.

FI942131 discloses a refractory mass for moulding of the inner parts of soap stone stoves, comprising a granular streamer spotted, magnesite and chlorite content talc schist as body substance. However, this invention solves the constructional problems regarding the design of the inner parts of soap stone stoves and does not aim to improve the heat-storing capacities for the stove. FI942131 teaches an alternative to know techniques in the field, where one previously used whole blocks of talc stone for the inner parts of the stoves.

Even though the refractory mass in FI942131 has advantageous properties during moulding of the inner parts of soap stone stoves and heat-storing capacities which in themselves are better than those for general building concrete, it is improper for the construction of floors, walls or roofs where the heat-storing capacity is particularly important. The refractory mass uses a refractory binding agent (preferably aluminium carbonate concrete) and also has a fine granule size (preferably less than 10 mm). These characteristics altogether make the mass too expensive to be considered for a large scale use such as production of concrete floors, walls or roofs in buildings and do not give any improvement of the thermal conductivity for the soap stone stove.

SUMMARY OF THE INVENTION

Consequently, in the circumstances of the above, the problem to provide a composition with good heat accumulating characteristics for construction of concrete floors, walls or roofs in buildings, which also is harmless to the environment and cost effective, remains.

The invention solves this by using a composition including ballast, hydraulic binding agent and water for construction of concrete floors, walls and roofs in buildings, in which the ballast in the concrete produced from the composition contains a sufficient amount of soap stone to achieve a concrete with higher specific heat capacity than for common concrete.

The term “common concrete” refers to concrete where the ballast is made out of sand or crushed gangue, granite/gneiss, common concrete or other commonly used ballast with low heat capacity.

The term “soap stone” refers as it is used herein to a group of magnesium containing species of stone with high thermal capacities. A person skilled in the art will understand that the amount of soap stone in the ballast can be adjusted from the desired heat capacity in the concrete, the material costs etc. It is preferred to use a high amount of soap stone in the ballast to ensure a high heat capacity. Further, it is specially preferred to use wastage and crushed material from large scale mining of soap stone, since this can be used in the invention in a cost effective and environment-friendly way.

Disregarding from the heat-storing capacity the characteristics for the ballast could be the same as for common concrete ballast, for example concerning the granule size (generally 0-32 mm in common concrete). Above all, it is possible to freely adjust the characteristics for the ballast and the concrete after the present requirements. The building composition may possibly also contain additives.

The composition can be used in several ways, for example to provide concrete mortar or pre-cast blocks or slabs. Generally, the composition is provided in the customary form for the use according to the invention.

The usage of the application entails several advantages. The improved heat-storing characteristics in the concrete according to the invention result in less energy need to warm up an area constructed of such concrete. When large amounts of energy easily can be stored, it is also possible to supply energy when the energy costs are lower and to, without any additional energy supply, let the energy emit when the energy costs are higher. The energy saving can be optimized additionally depending on the kind of energy supply system being used (e.g. ground source heat, heating floor of different kinds, district heating, different kinds of heating boilers etc.). All in all, a concrete prepared by using the composition according to the invention with good heat-storing characteristics is consequently provided for construction of floors, walls or roofs, which is also harmless to the environment and cost effective.

COMPARATIVE EXAMPLE

The following example serves only to illustrate the invention and shall not be considered limiting the inventive idea. The purpose of the example is to demonstrate that concrete provided with the composition according to the invention has better heat accumulating characteristics than common concrete.

Example 1

A 10 cm thick slab of concrete with a surface of about 0.3 m² was moulded of normal concrete mortar (grub-stone mortar marketed by Nacka Trä under the name “grovbetong”). Approximately 30% granite/gneiss of large size (up to 32 mm) was added to ensure that the size distribution for the ballast coincide with the concrete slab according to the invention.

Further, a 10 cm thick concrete slab with a surface of about 0.3 m² was moulded of concrete, water and approximately 60% soap stone, in which the soap stone had a size distribution of 0-32 mm. In both mouldings, standard techniques well known for a person skilled in the art were used.

Feed heat was delivered to both concrete slabs through heating tubes moulded-in in the slabs, by an electric boiler from CTC with built-in circulation pump. The temperature out in the heating tubes (at the outlet of the boiler) was a constant 24° C. The average temperature over moulded floor was measured 3 mm over the floor surface. The measurements were conducted during approximately two days with a thoroughly warm concrete slab, during which the following mean values were calculated:

Concrete slab with soap stone: 23.2° C.

Concrete slab with granite/gneiss: 22.5° C.

Further, measurements were made to determine how fast the two concrete slabs emitted the heat after cutting off the heat supply. After 24 h the temperature over the concrete slab with soap stone had dropped to 17.3° C. It took only 14 h for the temperature to drop to the same level over the concrete slab with granite/gneiss.

From these measurements the energy demand can be calculated to be approximately 6-10% higher for the concrete slab with granite/gneiss, without considering that the soap stone slab only contains 60% ballast. A ballast content of 75-80% (equivalent to the granite/gneiss concrete slab) would give even better heat characteristics. Further, it should be possible to lower the feeding temperature by one degree when soap stone concrete is used, since such a slab seems to carry the heat from the heating coils better.

During the experiments described above, some heat leakage occurred. The person skilled in the art shall therefore consider that, with more accurate measurements, it should be possible to demonstrate a greater difference for the heating characteristics between common concrete and the inventive composition. 

1. Method for using a composition comprising ballast, hydraulic binding agent and water for construction of concrete floors, walls or roofs in buildings, wherein the ballast in the concrete produced from the composition contains a sufficient amount of soap stone to achieve a concrete with higher specific heat capacity compared to common concrete.
 2. Method according to claim 1, in which the heat capacity for the concrete is higher than 0.95 kJ/kg·K.
 3. Method according to claim 2, in which the heat capacity for the concrete is higher than 1.00 kJ/kg·K.
 4. Method according to claim 3, in which the heat capacity for the concrete is higher than 1.05 kJ/kg·K.
 5. Method according to claim 1, in which the granule size for the ballast approximately is 0-32 mm.
 6. Method according to claim 1, in which the binding agent is Portland cement.
 7. Method according to claim 1, in which the concrete is concrete blocks for the construction of floors, walls or roofs.
 8. Method according to claim 1, in which the concrete is concrete slabs which are to be mounted on a surface. 